Silyl enol ethers trimethylsilyldiethylamine

Conjugate Addition. Conjugate addition of trimethylsilyl diethylamine to enones gives /3-amino silyl enol ethers. Thus, in the presence of catalytic amounts of trimethylsilyl triflate, trimethylsilyldiethylamine adds to ethyl vinyl ketone in a 1,4-fashion. The reaction requires 50 mol % excess of trimethylsilyldiethylamine, and proceeds in ether at room temperature under nitrogen. The product Af,A -diethyl-3-[(tiimethylsilyl)oxy]-( )-2-pentamine is distilled out under reduced pressure in 45% yield (eq 18). The major product is the -enol ether containing approximately 5% of other trimethylsilyl ether isomers. 

Enamine and Silyl Enol Ether Preparation. Both enamines and silyl enol ethers are useful intermediates in organic s)fnthe-sis. Aldehydes and ketones can be transformed into enamines via treatment with 2-3 equiv of trimethylsilyldiethylamine in the presence of a trace of / -toluenesulfonic acid. The presence of excess silylamine obviates the normal requirements for water removal by azeotropic distillation or by addition of an insoluble drying agent. No solvent or heating is required for the transformation, and the reaction normally proceeds at room temperature. However, heating the reaction mixture allows enamine synthesis in equally high yield without an acid catalyst. 

Nevertheless, silyl enol ethers can be conveniently prepared by the reaction of ketones with trimethylsilyldiethylamine and methyl iodide. The process involves heating a mixture of 1.2 equiv of trimethyl silyldiethylamrne and 1.3 equiv of methyl iodide at 60 °C for 1 h, and subsequently ketone is added dropwise (eqs 22 and 23). ... 

The combination of trimethylsilyldiethylamine and methyl iodide transforms both the cyclic and the acyclic ketones into silyl enol ethers in high yield, with favored formation of the more thermodynamically stable isomer. 

Trimethylpyridine, 61, 62 N-Trimethylsilylamides, 204 Trimethylsilyl azide, 276, 542 Trimethylsilylcarbene, 544 Trimethylsilyl cyanide, 542-543 Trimethylsilyldiazomethane, 543-544 Trimethylsilyldiethylamine, 544-545 Trimethylsilyl enol ethers, 125, 538 N-(Trimethylsilyl)glycine trimethyl silyl... 

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See also in sourсe #XX -- [ ]

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